This invention relates to heat sinks having good heat-dissipating properties that are manufactured by cold forging, warm forging, hot forging or combinations of these methods with alkali dissolution. More particularly, it relates to so-called pin-finned heat sinks having pin-shaped cooling fins. The invention also relates to a process for producing pin-finned heat sinks.
Efforts to increase the level of integration in semiconductor devices have progressed so remarkably that devices have emerged today that consume power of 35 watts or more per chip. In order to operate such high-power semiconductor devices with high reliability, the heat generated by the devices must be dissipated to the exterior in an efficient manner. To this end, highly integrated semiconductor devices are fitted with a heat sink having cooling fins.
Heat sinks in common use today are of two types, one having cooling fins of a channel type in which plane parallel plates are arranged in a comb shape, and the other having cooling fins of a tower type in which a plurality of disks are stacked in a tower form. Both types of cooling fins are manufactured by a machining method, so limitations on the thickness of the bite used and difficulties in the processing of cuttings unavoidably increases production costs.
Inexpensive cooling fins of a channel type are produced by hot extrusion, but with this method, the thickness and pitch of the fins are limited to such an extent that only heat sinks having poor dissipating characteristics can be produced.
Many years ago, researchers took an interest in the dissipating characteristics of pin-finned heat sinks, especially their leading edge effects. Subsequently, several reports were published on the manufacture of pin-finned heat sinks by mold casting, machining, or even cold forging. Although a considerable time has since passed, the production of such pin-finned heat sinks has not yet met substantial commercial success on an industrial scale.
Mold casting and machining methods are incapable of producing the desired heat sinks with satisfactory efficiency. On the other hand, with cold forging, it is difficult to assure good cold forming, namely, effective plastic working. Furthermore, whichever method is employed, the heat dissipating characteristics of the resulting pin-finned heat sinks are no better than those of the existing heat sinks in common use today.